Browser-wide audio mirroring for TabCapture API

media/audio/audio_manager_base.cc

Index: media/audio/audio_manager_base.cc
diff --git a/media/audio/audio_manager_base.cc b/media/audio/audio_manager_base.cc
index eca877311558b6d421ac59d0d83b3007177869ad..59f885695add792830a85ec0f012ad6cc0067322 100644
--- a/media/audio/audio_manager_base.cc
+++ b/media/audio/audio_manager_base.cc
@@ -14,6 +14,8 @@
 #include "media/audio/audio_util.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/audio/fake_audio_output_stream.h"
+#include "media/audio/virtual_audio_input_stream.h"
+#include "media/audio/virtual_audio_output_stream.h"
 #include "media/base/media_switches.h"
 
 // TODO(dalecurtis): Temporarily disabled while switching pipeline to use float,
@@ -45,7 +47,8 @@ AudioManagerBase::AudioManagerBase()
       max_num_input_streams_(kDefaultMaxInputStreams),
       num_output_streams_(0),
       num_input_streams_(0),
-      audio_thread_(new base::Thread("AudioThread")) {
+      audio_thread_(new base::Thread("AudioThread")),
+      virtual_audio_input_stream_(NULL) {
 #if defined(OS_WIN)
   audio_thread_->init_com_with_mta(true);
 #endif
@@ -100,7 +103,16 @@ AudioOutputStream* AudioManagerBase::MakeAudioOutputStream(
       !HasAudioOutputDevices();
 
   AudioOutputStream* stream = NULL;
-  if (audio_output_disabled) {
+  if (virtual_audio_input_stream_) {
+#if defined(OS_IOS)
+    // We do not currently support iOS. It does not link.
+    NOTIMPLEMENTED();
+    return NULL;
+#else
+    stream = VirtualAudioOutputStream::MakeStream(this, params,
+        virtual_audio_input_stream_);
+#endif
+  } else if (audio_output_disabled) {
     stream = FakeAudioOutputStream::MakeFakeStream(this, params);
   } else if (params.format() == AudioParameters::AUDIO_PCM_LINEAR) {
     stream = MakeLinearOutputStream(params);
@@ -130,7 +142,31 @@ AudioInputStream* AudioManagerBase::MakeAudioInputStream(
   }
 
   AudioInputStream* stream = NULL;
-  if (params.format() == AudioParameters::AUDIO_FAKE) {
+  if (params.format() == AudioParameters::AUDIO_VIRTUAL) {
+  #if defined(OS_IOS)

[DaleCurtis, 2012/12/03 19:27:28]

#if is never indented.

[justinlin, 2012/12/03 21:18:42]

Done.

+    // We do not currently support iOS.
+    NOTIMPLEMENTED();
+    return NULL;
+  #else
+    // TODO(justinlin): Currently, audio mirroring will only work for the first
+    // request. Subsequent requests will not get audio.
+    if (!virtual_audio_input_stream_) {
+      virtual_audio_input_stream_ =
+          VirtualAudioInputStream::MakeStream(this, params);
+      stream = virtual_audio_input_stream_;
+      DVLOG(1) << "Virtual audio input stream created.";
+
+      // Make all current output streams recreate themselves as
+      // VirtualAudioOutputStreams that will attach to the above
+      // VirtualAudioInputStream.
+      message_loop_->PostTask(FROM_HERE, base::Bind(
+          &AudioManagerBase::NotifyAllOutputDeviceChangeListeners,

[DaleCurtis, 2012/12/03 19:27:28]

I mentioned this to Yuri, but FYI, we'll probably start filtering these changes
to only fire when hardware output values actually change.  It should be simple
enough to always fire if virtual_audio_input_stream_ is set though.

[justinlin, 2012/12/03 21:18:42]

Acknowledged.

[DaleCurtis, 2012/12/03 21:30:56]

The previous style here was fine. You can always switch to 4 space indent when
providing for a new function.

[justinlin, 2012/12/03 22:01:48]

Done. OK, I see.

+          base::Unretained(this)));
+    } else {
+      stream = NULL;
+    }
+  #endif
+  } else if (params.format() == AudioParameters::AUDIO_FAKE) {
     stream = FakeAudioInputStream::MakeFakeStream(this, params);
   } else if (params.format() == AudioParameters::AUDIO_PCM_LINEAR) {
     stream = MakeLinearInputStream(params, device_id);
@@ -244,6 +280,17 @@ void AudioManagerBase::ReleaseOutputStream(AudioOutputStream* stream) {
 void AudioManagerBase::ReleaseInputStream(AudioInputStream* stream) {
   DCHECK(stream);
   // TODO(xians) : Have a clearer destruction path for the AudioInputStream.
+
+  if (virtual_audio_input_stream_ == stream) {
+    DVLOG(1) << "Virtual audio input stream stopping.";
+    virtual_audio_input_stream_->Stop();
+    virtual_audio_input_stream_ = NULL;
+
+    // Make all audio output streams (which should be virtual) recreate
+    // themselves as regular audio streams to return sound to hardware.
+    NotifyAllOutputDeviceChangeListeners();

[DaleCurtis, 2012/12/03 19:27:28]

Should this be PostTask'd?

[justinlin, 2012/12/03 21:18:42]

No, I don't think so. We need the output streams to detach first before we
delete the virtual audio input stream.

+  }
+
   num_input_streams_--;
   delete stream;
 }